Battery based on organosulfur species

ABSTRACT

Metal-sulfur batteries, such as lithium-sulfur batteries, are prepared using one or more organosulfur species such as organic polysulfides and organic polythiolates as part of the liquid or gel electrolyte solution, as part of the cathode, and/or as part of a functionalized porous polymer providing an intermediate separator element.

FIELD OF THE INVENTION

The invention relates to batteries having an anode based on sodium,lithium or mixture thereof or alloy or composite of sodium and/orlithium with one or more other metals and a cathode based on elementalsulfur, selenium, or mixture of elemental chalcogens, the anode andcathode being separated by a separator element with a liquid or gelelectrolyte solution of a conductive salt in a nonaqueous polar aproticsolvent or polymer in contact with the electrodes.

BACKGROUND OF THE INVENTION

Electrochemical batteries are a principal means for storing anddelivering electrical energy. Due to increasing demands for energy forelectronic, transportation and grid-storage applications, the need forbatteries with ever more power storage and delivery capability willcontinue long into the future.

Because of their light weight and high energy storage capacity ascompared to other types of batteries, lithium ion batteries have beenwidely used since the early 1990's for portable electronic applications.However, current Li-ion battery technology does not meet the high powerand energy needs for large applications such as grid storage or electricvehicles with driving ranges that are competitive with vehicles poweredby internal combustion engines. Thus, extensive efforts in thescientific and technical communities continue to identify batteries withhigher energy density and capacity.

Sodium-sulfur and lithium-sulfur electrochemical cells offer even highertheoretical energy capacity than Li-ion cells and thus have continued toelicit interest as “next-generation” battery systems. Electrochemicalconversion of elemental sulfur to the monomeric sulfide (S²⁻) offers atheoretical capacity of 1675 mAh/g as compared to less than 300 mAh/gfor Li-ion cells.

Sodium-sulfur batteries have been developed and launched as commercialsystems. Unfortunately, the sodium-sulfur cell typically requires hightemperatures (above 300° C.) to be functional, and thus is only suitablefor large stationary applications.

Lithium-sulfur electrochemical cells, initially proposed in the late1950's and 1960's, are only now being developed as commercial batterysystems. These cells offer theoretical specific energy densities above2500 Wh/kg (2800 Wh/L) vs. 624 Wh/g for lithium ion. The demonstratedspecific energy densities for Li—S cells are in the range of 250-350Wh/kg, as compared to 100 Wh/g for Li-ion cells, the lower values beingthe result of specific features of the electrochemical processes forthese systems during charge and discharge. Given that the practicalspecific energies of lithium batteries are typically 25-35% of thetheoretical value, the optimum practical specific energy for a Li—Ssystem would be around 780 Wh/g (30% theoretical). [V. S. Kolosnitsyn,E. Karaseva, US Patent Application 2008/0100624 A1]

The lithium-sulfur chemistry offers a number of technical challengesthat have hindered the development of these electrochemical cells,particularly poor discharge-charge cyclability. Nonetheless, because ofthe inherent low weight, low cost, high power capacity of thelithium-sulfur cell, great interest exists in improving the performanceof the lithium-sulfur system and extensive work has been performed inthe last 20 years by many researchers all over the world to addressthese issues. [C. Liang, et al. in Handbook of Battery Materials 2^(nd)Ed., Chapter 14, pp. 811-840 (2011); V. S. Kolosnitsyn, et al., J. PowerSources 2011, 196, 1478-82; and references therein.]

A cell design for a lithium-sulfur system typically includes:

-   -   An anode consisting of lithium metal, lithium-alloy or        lithium-containing composite materials.    -   A non-reactive but porous separator between the anode and        cathode (often polypropylene or -alumina). The presence of this        separator results in separate anolyte and catholyte        compartments.    -   A porous sulfur-bearing cathode that incorporates a binder        (often polyvinylidene difluoride) and a conductivity-enhancing        material (often graphite, mesoporous graphite, multiwall carbon        nanotubes, graphene),    -   An electrolyte consisting of a polar aprotic solvent and one or        more conductive Li salts [(CF₃SO₂)₂N⁻, CF₃SO₃ ⁻, CH₃SO₃ ⁻, ClO₄        ⁻, PF₆ ⁻, AsF₆ ⁻, halogens, etc.]. The solvents used in these        cells have included basic (cation-complexing) aprotic polar        solvents such as sulfolane, dimethyl sulfoxide,        dimethylacetamide, tetramethyl urea, N-methyl pyrrolidinone,        tetraethyl sulfamide, tetrahydrofuran, methyl-THF,        1,3-dioxolane, diglyme, and tetraglyme. Lower polarity solvents        are not suitable due to poor conductivity and poor ability to        solvate Li⁺ species, and protic solvents can react with Li        metal. In solid-state versions of the lithium-sulfur cell, the        liquid solvents are replaced with a polymeric material such as        polyethylene oxide.    -   Current collectors and appropriate casing materials.

SUMMARY OF THE INVENTION

Compositions and applications of organic polysulfides and organicpolythiolates for use in metal-sulfur batteries, particularlylithium-sulfur batteries, are provided by the present invention. Theorganic polysulfide and organopolythiolate species act to improve theperformance of such electrochemical cells during repeated discharge andcharge cycles.

The present invention thus relates to chemical sources of energycomprising a cell or battery with one or more positive electrodes(cathodes), one or more negative electrodes (anodes) and an electrolytemedia, wherein the operative chemistry involves reduction of sulfur orpolysulfide species and oxidation of the reactive metal species. Thenegative electrode comprises a reactive metal such as lithium, sodium,potassium or alloys/composites of those metals with other materials. Thepositive electrode comprises sulfur, organic polysulfide species, and/ormetal organic polysulfide salts, and matrices containing these species.The electrolyte matrices comprise mixtures of organic solvent orpolymers, inorganic or organic polysulfide species, carriers for theionic form of the active metal, and other components intended tooptimize electrochemical performance.

Specifically, this invention relates to the use of organic polysulfides,and their lithium (or sodium, quaternary ammonium or quaternaryphosphonium) organothiolate or organopolythiolate analogs, as componentsin the cathode and electrolyte matrices. Said organosulfur specieschemically combine with sulfur and anionic mono- or polysulfide speciesto form organopolythiolate species which have increased affinity for thenonpolar sulfur components of the positive cathode and catholyte phase.

One aspect of the invention provides a battery, the battery comprising:

-   -   a) an anode comprising an anode active material comprising        sodium, lithium or an alloy or composite of at least one of        sodium or lithium with at least one other metal for providing        ions;    -   b) a cathode comprising a cathode active material comprising        elemental sulfur, elemental selenium or a mixture of elemental        chalcogens; and    -   c) an intermediate separator element positioned between the        anode and cathode acting to separate liquid or gel electrolyte        solutions in contact with the anode and cathode, through which        metal ions and their counterions move between the anode and        cathode during charge and discharge cycles of the battery;    -   wherein the liquid or gel electrolyte solutions comprise a        nonaqueous polar aprotic solvent or polymer and a conductive        salt and at least one of conditions (i), (ii) or (iii) are met:    -   (i) at least one of the liquid or gel electrolyte solutions        additionally comprise at least one organosulfur species;    -   (ii) the cathode is additionally comprised of at least one        organosulfur species;    -   (iii) the intermediate separator element comprises a        functionalized porous polymer containing at least one        organosulfur species;    -   wherein the organosulfur species comprises at least one organic        moiety and at least one —S—S_(n)— linkage, with n being an        integer of 1 or more.

In one embodiment, just one of conditions (i), (ii) or (iii) is met. Inanother embodiment, all three conditions are met. In still anotherembodiment, only two of the conditions are met, e.g., (i) and (ii), (i)and (iii), or (ii) and (iii).

In another aspect, the invention provides an electrolyte comprising atleast one nonaqueous polar aprotic solvent or polymer, at least oneconductive salt, and at least one organosulfur species comprised of atleast one organic moiety and at least one —S—S_(n)— linkage wherein n isan integer of 1 or more.

Another aspect of the invention provides a cathode comprising a)elemental sulfur, elemental selenium or a mixture of elementalchalcogens, b) at least one electrically conductive additive, c) and atleast one organosulfur species comprising at least one organic moietyand at least one —S—S_(n)— linkage, n being an integer of 1 or more.

The organosulfur species, for example, may be selected from the groupconsisting of organic polysulfides and/or metal organic polythiolates.In certain embodiments of the invention, the organosulfur speciescontains one or more sulfur-containing functional groups selected fromthe group consisting of dithioacetal, dithioketal,trithio-orthocarbonate, thiosulfonate [—S(O)₂—S-], thiosulfinate[—S(O)—S-], thiocarboxylate [—C(O)—S-], dithiocarboxylate [—C(S)—S-],thiophosphate, thiophosphonate, monothiocarbonate, dithiocarbonate, andtrithiocarbonate. In other embodiments, the organosulfur species may beselected from the group consisting of aromatic polysulfides,polyether-polysulfides, polysulfide-acid salts and mixtures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows discharge profiles of lithium-sulfur battery withn-C12H25SLi added to the cathode for repeated charge/discharge cycles 3to 63.

DETAILED DESCRIPTION OF THE INVENTION

An electroactive material that has been fabricated into a structure foruse in a battery is referred to as an electrode. Of a pair of electrodesused in a battery, which serves as a chemical source of electricalenergy, the electrode on the side having a higher electrochemicalpotential is referred to as the positive electrode, or the cathode,while the electrode on the side having a lower electrochemical potentialis referred to as the negative electrode, or the anode. As used herein,the conventional nomenclature for batteries is employed wherein theterms “cathode” or “positive electrode” and “anode” or “negativeelectrode” refer to the electrochemical functions of the electrodesduring discharge of the cell to provide electrical energy. During thecharging portion of the cycle, the actual electrochemical functions ofan electrode are reversed versus that which occurs during discharge, butthe designation of the respective electrodes remains the same as fordischarge.

Electrochemical cells are commonly combined in series, the aggregate ofsuch cells being referred to as a battery. Based on the operativechemistry of the cells, primary batteries are designed for a singledischarge to provide power for an external device. Secondary batteriesare rechargeable, using electrical energy from an external source, andthus offer extended use over multiple discharge and charge cycles.

An electrochemically active material used in the cathode or positiveelectrode is referred to hereinafter as a cathode active material. Anelectrochemically active material used in the anode or negativeelectrode is hereinafter referred to as an anode active material.Multi-component compositions possessing electrochemical activity andcomprising an electrochemically active material and optionalelectrically conductive additive and binder, as well as other optionaladditives, are referred to hereinafter as electrode compositions. Abattery comprising a cathode with the cathode active material in anoxidized state and an anode with the anode active material in a reducedstate is referred to as being in a charged state. Accordingly, batterycomprising a cathode with the cathode active material in a reducedstate, and an anode with the anode active material in an oxidized state,is referred to as being in a discharged state.

Without wishing to be bound by theory, the following are certainpossible advantages or features of the present invention. Theorganosulfur species may partition to the sulfur-rich catholyte phase.The chemical exchange reactions between dianionic sulfides orpolysulfides (e.g., Li₂S_(x), x=1, 2, 3 . . . ) and theorganopolysulfides or organopolythiolates (e.g., R—S_(x)—R orR—S_(x)—Li, R and R′=organic moieties), along with sulfurextrusion/reinsertion chemistries common to polysulfides andpolythiolates, favor minimizing the amount of the dianionic polysulfidesin the catholyte and favor redeposition of sulfur and sulfur-containingspecies at the cathode. The net removal of the dianionic polysulfideswould reduce the electrolyte viscosity and thus minimize the deleteriouseffects of high viscosity on electrolyte conductivity. The organosulfurspecies may also increase the dissolution, and thus scavenging, ofinsoluble low-rank lithium sulfide species (particularly Li₂S and Li₂S₂)in both the catholyte and anolyte phases, thus minimizing loss ofreactive lithium species upon repeated charge/discharge cycles. Theperformance of the organosulfur species can be “tuned” by selection ofthe organic functionality. For example, short chain alkyl or alkylgroups with more polar functionality, would partition more to theanolyte phase, while the longer-chain or less-polar analogs wouldpartition more to the catholyte phase. Adjusting the relative ratios ofthe long/nonpolar and short/polar chain organic species would provide ameans of controlling the partition of sulfur-containing species to thecathode/catholyte. Moreover, since the presence of some amount ofpolysulfide or polythiolate in the anolyte is advantageous as a means ofcontrolling lithium dendrite growth on the anode during charging,selection of appropriate organic moieties and their relative ratioswould provide greater control of dendrite growth.

Organosulfur species useful in the present invention comprise at leastone organic moiety and at least one —S—S_(n)— linkage, wherein n is aninteger of at least 1. In one embodiment, the organosulfur speciescomprises two organic moieties per molecule (which may be the same as ordifferent from each other) which are linked by a —S—S_(n)— (polysulfide)linkage (wherein n is an integer of 1 or more). The —S—S_(n)— linkagemay form part of a larger linking group such as a —Y¹—C(Y²Y³)—S—S_(n)—linkage or a —Y¹—C(═Y⁴)—S—S_(n)— linkage, wherein Y is O or S, Y² and Y³are independently an organic moiety or —S—S_(o)—Z, where o is 1 or moreand Z is an organic moiety or a species selected from Li, Na, quaternaryammonium, or quaternary phosphonium, and Y⁴ is O or S. In anotherembodiment, the organosulfur species contains a monovalent organicmoiety and a species selected from Na, Li, quaternary ammonium andquaternary phosphonium which are linked by a —S—S_(n)— linkage(including, for example, a —Y¹—C(Y²Y³)—S—S_(n)— linkage or—Y¹—C(═Y⁴)—S—S_(n)— linkage). In still another embodiment, a —S—S_(n)—linkage may appear on either side of an organic moiety. For example, theorganic moiety can be a divalent, optionally substituted aromaticmoiety, C(R³)₂ (with each R³ being independently H or an organic moietysuch as a C₁-C₂₀ organic moiety), carbonyl(C═O) or thiocarbonyl(C═S).

The organosulfur species may, for example, be selected from the groupconsisting of organic polysulfides, organic polythiolates, includingthose with sulfur-containing functional groups such as dithioacetal,dithioketal, trithio-orthocarbonate, aromatic polysulfide,polyether-polysulfide, polysulfide-acid salt, thiosulfonate [—S(O)₂—S-],thiosulfinate [—S(O)—S-], thiocarboxylate [—C(O)—S-], dithiocarboxylate[—RC(S)—S-], thiophosphate or thiophosphonate functionality, or mono-,di- or trithiocarbonate functionality; organo-metal polysulfidescontaining these or similar functionalities; and mixtures thereof.

Suitable organic moieties include, for example, mono-, di- andpolyvalent organic moieties which may comprise branched, linear and/orcyclic hydrocarbyl groups. As used herein, the term “organic moiety”includes a moiety which may, in addition to carbon and hydrogen,comprise one or more heteroatoms such as oxygen, nitrogen, sulfur,halogen, phosphorus, selenium, silicon, a metal such as tin and thelike. The heteroatom(s) may be present in the organic moiety in the formof a functional group. Thus, hydrocarbyl as well as functionalizedhydrocarbyl groups are considered within the context of the presentinvention to be organic moieties. In one embodiment, the organic moietyis a C₁-C₂₀ organic moiety. In another embodiment, the organic moietycontains two or more carbon atoms. The organic moiety thus may be aC₂-C₂₀ organic moiety.

The organosulfur species may be monomeric, oligomeric or polymeric incharacter. For example, the —S—S_(n)— functionality may be pendant tothe backbone of an oligomeric or polymeric species containing two ormore repeating units of monomer in its backbone. The —S—S_(n)—functionality may be incorporated into the backbone of such an oligomeror polymer, such that the oligomer or polymer backbone contains aplurality of —S—S_(n)— linkages.

The organosulfur species may, for instance, be an organic polysulfide ormixture of organic polysulfides of formula R¹—S—S_(n)—R², wherein R¹ andR² independently represent a C₁-C₂₀ organic moiety and n is an integerof 1 or more. The C₁-C₂₀ organic moiety may be a monovalent branched,linear or cyclic hydrocarbyl group. R¹ and R² may each independently bea C₉-C₁₄ hydrocarbyl group, with n=1 (providing a disulfide, such astertiary-dodecyl disulfide). In another embodiment, R¹ and R² are eachindependently a C₉-C₁₄ hydrocarbyl group, with n=2-5 (providing apolysulfide). Examples of such compounds include TPS-32 and TPS-20, soldby Arkema. In another embodiment, R¹ and R² are independently C₇-C₁₁hydrocarbyl groups, with n=2-5. TPS-37LS, sold by Arkema, is an exampleof a suitable polysulfide of this type. Another type of suitablepolysulfide would be a polysulfide or mixture of polysulfides wherein R¹and R² are both tert-butyl and n=2-5. Examples of such organosulfurcompounds include TPS-44 and TPS-54, sold by Arkema.

The organosulfur species could also be an organic polythiolate offormula R¹—S—S_(n)-M, wherein R¹ is a C₁-C₂₀ organic moiety, M islithium, sodium, quaternary ammonium, or quaternary phosphonium and n isan integer of 1 or more.

In another embodiment, the organosulfur species may be a dithioacetal ordithioketal such as those corresponding to formulas (I) and (II), or atrithio-orthocarboxylate of formula (III):

wherein each R³ is independently H or a C₁-C₂₀ organic moiety, o, p andq are each independently an integer of 1 or more, and each Z isindependently a C₁-C₂₀ organic moiety, Li, Na, quaternary ammonium, orquaternary phosphonium. Examples of such organosulfur species include1,2,4,5-tetrathiane (formula I, R³═H, o=p=1),tetramethyl-1,2,4,5-tetrathiane (formula I, R³═CH₃, o=p=1), and oligo orpolymeric species thereof.

Another embodiment of the invention utilizes an organosulfur specieswhich is an aromatic polysulfide of formula (IV), apolyether-polysulfide of formula (V), a polysulfide-acid salt of formula(VI), or a polysulfide-acid salt of formula (VII):

wherein R⁴ independently is tert-butyl or tert-amyl, R⁵ independently isOH, OLi or ONa, and r is 0 or more (e.g., 0-10) in formula (IV) with thearomatic rings being optionally substituted in one or more otherpositions with substituents other than hydrogen, R⁶ is a divalentorganic moiety in formula (VI), R⁷ is a divalent organic moiety informula (VII), each Z is independently a C₁-C₂₀ organic moiety, Li, Na,quaternary ammonium or quaternary phosphonium, and o and p are eachindependently an integer of 1 or more. Examples of such organosulfurspecies include the aromatic polysulfides sold by Arkema under the brandname Vultac®(formula IV, R⁴=tert-butyl or tert-amyl, R⁵═OH); andpolysulfide-acid salts corresponding to formulas VI and VII derived frommercapto-acids such as mercaptoacetic acid, mercaptopropionic acid,mercaptoethanesulfonic acid, mercaptopropanesulfonic acid, or fromolefin-containing acids such as vinylsulfonic acid or2-acrylamido-2-methylpropanesulfonic acid.

In still another embodiment, the organosulfur species is an organo- ororgano-metal polysulfide containing trithiocarbonate functionality offormula (IX), an organo- or organo-metal polysulfide containingdithiocarbonate functionality of formula (X), or an organo- ororgano-metal polysulfide containing monothiocarbonate functionality offormula (XI):

wherein Z is a C₁-C₂₀ organic moiety, Na, Li, quaternary ammonium, orquaternary phosphonium, and o and p are independently an integer of 1 ormore.

The liquid or gel electrolyte solution may be additionally comprised ofa dimetal polythiolate species of formula M-S—S_(n)-M, wherein each M isindependently Li, Na, quaternary ammonium, or quaternary phosphonium andn is an integer of 1 or more. Such a species thus does not contain anyorganic moiety, unlike the above-described organosulfur species.

The intermediate separator element may function as a divider betweencompartments in an electrochemical cell. One compartment may comprise anelectrolyte in contact with a cathode (the electrolyte in suchcompartment may be referred to as a catholyte). Another compartment maycomprise an electrolyte in contact with an anode (the electrolyte insuch compartment may be referred to as an anolyte). The anolyte and thecatholyte may be the same as, or different from, each other. One or bothof the anolyte and the catholyte may contain one or more organosulfurspecies in accordance with the present invention. The intermediateseparator element may be positioned between such compartments in amanner so as to permit ions from the anolyte to pass through theintermediate separator element into the catholyte and vice versa,depending upon whether the electrochemical cell is being operated in thecharge or discharge mode.

In a further embodiment of the invention, the intermediate separatorelement is comprised of a porous polymer. The porous polymer may, forexample, be comprised of polypropylene, polyethylene, or a fluorinatedpolymer. The porous polymer may be functionalized with an organosulfurspecies of the type described herein. The organosulfur species may bependant to the backbone of the porous polymer, may be present incrosslinks between the backbones of individual polymer chains and/or maybe incorporated into the backbone of the porous backbone. Thus, thebackbone of the porous polymer may contain one or more —S—S_(n)—linkages and/or —S—S_(n)— linkages may be pendant to the polymerbackbone. Such —S—S_(n)— linkages may also be present in crosslinks.

Suitable solvents to be used in electrochemical cells in accordance withthe invention include any of the basic (cation-complexing) aprotic polarsolvents known or used for lithium-sulfur batteries generally such assulfolane, dimethyl sulfoxide, dimethylacetamide, tetramethyl urea,N-methyl pyrrolidinone, tetraethyl sulfamide; ethers such astetrahydrofuran, methyl-THF, 1,3-dioxolane, diglyme, and tetraglyme, andmixtures thereof; carbonates such as ethylene carbonate, propylenecarbonate, dimethylcarbonate, diethylcarbonate, ethylmethylcarbonate,methylpropylcarbonate, ethylpropylcarbonate and the like; as well asesters such as methylacetate, ethyl acetate, propylacetate, andgamma-butyrolactone. The electrolyte may comprise a single such solventor a mixture of such solvents. Any of the polar aprotic polymers knownin the battery art could also be employed. The electrolyte may comprisea polymeric material and may take the form of a gel. Suitable polymersfor use in the electrolyte may include, for example, polyethylene oxide,a polyethersulfone, a polyvinylalcohol, or a polyimide. The electrolytemay be in the form of a gel, which may be a three-dimensional networkcomprised of a liquid and a binder component. The liquid may be amonomeric solvent which is entrained within a polymer, such as acrosslinked polymer.

One or more conductive salts are present in the electrolyte incombination with the nonaqueous polar aprotic solvent and/or polymer.Conductive salts are well known in the battery art and include, forexample, lithium salts of (CF₃SO₂)₂N⁻, CF₃SO₃ ⁻, CH₃SO₃ ⁻, ClO₄ ⁻, PF₆⁻, AsF₆ ⁻, halogen or the like. Sodium and other alkali metal salts andmixtures thereof may also be used.

The anode active material may comprise an alkali metal such as lithiumor sodium or another active material or composition. Particularlypreferred anode active materials include metallic lithium, alloys oflithium, metallic sodium, alloys of sodium, alkali metals or alloysthereof, metal powders, alloys of lithium and aluminum, magnesium,silicon, and/or tin, alkali metal-carbon and alkali metal-graphiteintercalates, compounds capable of reversibly oxidizing and reducingwith an alkali metal ion, and mixtures thereof. The metal or metal alloy(e.g., metallic lithium) may be contained as one film within a batteryor as several films, optionally separated by a ceramic material.Suitable ceramic materials include, for example, silica, alumina, orlithium-containing glassy materials such as lithium phosphates, lithiumaluminates, lithium silicates, lithium phosphorus oxynitrides, lithiumtantalum oxide, lithium aluminosilicates, lithium titanium oxides,lithium silicosulfides, lithium germanosulfides, lithiumaluminosulfides, lithium borosulfides, lithium phosphosulfides andmixtures thereof.

The cathode comprises elemental sulfur, elemental selenium or a mixtureof elemental chalcogens. In one embodiment, the cathode is additionallycomprised of one or more organosulfur species in accordance with thosepreviously described in detail herein. The cathode may additionallyand/or alternatively be comprised of a binder and/or an electricallyconductive additive. Suitable binders include polymers such as, forexample, polyvinyl alcohol, polyacrylonitrile, polyvinylidene fluoride(PVDF), polyvinyl fluoride, polytetrafluoroethylene (PTFE), copolymersfrom tetrafluoroethylene and hexafluoropropylene, copolymers fromvinylidene fluoride and hexafluoropropylene, copolymers from vinylidenefluoride and tetrafluoroethylene, ethylene-propylene-diene monomerrubber (EPDM), and polyvinyl chloride (PVC). The electrically conductiveadditive may be, for example, a carbon in electrically conductive formsuch as graphite, graphene, carbon fibers, carbon nanotubes, carbonblack, or soot (e.g., lamp or furnace soot). The cathode may be presentin a battery or electrochemical cell in combination with a currentcollector, such as any of the current collectors known in the battery orelectrochemical cell art. For example, the cathode may be coated on thesurface of a metallic current collector.

EXAMPLES Cathode Fabrication, Battery Preparation, and Battery TestingExample 1

A positive electrode comprising 70 wt % sublimed elemental sulfurpowder, 20 wt % polyethylene oxide (PEO, MW 4×10⁶), 10 wt % carbon black(Super P® Conductive, Alfa Aesar) was produced by the followingprocedure:

The mixture of these components in N-methyl-2-pyrrolidone (NMP) wasmechanically ground in a planetary milling machine. Acetonitrile wasadded to dilute the mixture. The resulting suspension was applied ontoaluminum foil (76 μm thickness) with an automatic film coater (Mathis).The coating was dried at 50° C. in a vacuum oven for 18 hrs. Theresulting coating contained 3.10 mg/cm² cathode mixture.

Example 2

A positive cathode containing lithium n-dodecyl mercaptide (10 wt % ofsulfur) was prepared following the procedure described in Example 1. Theresulting coating contained 3.4 mg sulfur/cm²

Example 3

The positive cathode from Example 2 was used in a PTFE Swaglok cell withtwo stainless steel rods or coin cell assembly made of stainless steel(CR2032). The battery cell was assembled in an argon filled glove box(MBraun) as follows: the cathode electrode was placed on the bottom canfollowed by the separator. Then electrolyte was added to the separator.A lithium electrode was placed onto of the separator. A spacer and aspring were placed on top of the lithium electrode. The battery core wassealed with the stainless steel rods or with a crimping machine.

Example 4

Following the procedure described in Example 3, a battery cellconsisting of cathode from Example 2 ( 7/16″ diameter), 20 μL of 0.5 MLiTFSI solution in tetraethylene glycol dimethyl ether (TEGDME):1,3-dioxolane (DOL)=1:1, separator, and lithium electrode (thickness0.38 mm, diameter 7/16″) was tested for charge-discharge cycling at acurrent of 0.1 mA. The testing was carried out using Gamry potentiometer(Gamry Instruments) to cut-off voltage of 1.5 V and 3.2 V at roomtemperature. The discharge cycle profile is illustrated in FIG. 1.

Syntheses of Lithium Alkylmercaptides Example 5 Synthesis of Lithiumn-Dodecyl Mercaptide with Hexyl Lithium

To n-dodecyl mercaptan (9.98 g, 1 eq.) in hexanes (100 mL) at −30° C.was added n-hexyllithium (33 wt % in hexane, 1.1 eq.) dropwise tomaintain mixture temperature below −20° C. The solvent was removed underreduced pressure to yield a white solid at quantitative yield.

Example 6 Synthesis of Lithium n-Dodecyl Mercaptide with LithiumHydroxide

A mixture of n-dodecyl mercaptan (2.0 g, 1 eq.) and lithium hydroxidemonohydrate (0.41 g, 1 eq.) in acetonitrile (8 mL) was heated to 75° C.and stirred at 75° C. for 16 hrs. After cooling to room temperature, thereaction mixture was filtered. The filter cake was rinsed withacetonitrile and dried at 50° C. in a vacuum oven over night. Thelithium n-dodecylmercaptide was obtained as a white solid in 93.5% yield(1.93 g)

Example 7 Synthesis of Lithium n-Dodecyl Mercaptide with Hexyl Lithium

Following the procedure described in Example6,3,6-dioxaoctane-1,8-dithiol di-lithium salt was synthesized from thedi-mercaptan as a white solid in quantitative yield.

Syntheses of Lithium Alkyl Polythiolates Example 8 Synthesis of Lithiumn-Dodecylpolythiolate with Lithium Hydroxide

To a nitrogen degassed solution of n-dodecyl mercaptan (2.00 g, 1 eq.)in 1,3-dioxolane (25 mL) was added lithium hydroxide monohydrate (0.41g, 1 eq.) and sulfur (1.27 g, 4 eq.). The mixture was stirred undernitrogen at room temperature for 30 min. Lithium n-dodecyl polythiolatein 1,3-dioxolane was obtained as a dark red solution. Completeconversion of mercaptan to lithium n-dodecyl polythiolate was confirmedby ¹³C-NMR and LCMS.

Example 9 Synthesis of Lithium 3,6-Dioxaoctane-1,8-Polythiolate withLithium Hydroxide and Sulfur

Following the procedure described in Example 8, dark red solution oflithium 3,6-dioxaoctane-1,8-polythiolate in 1,3-dioxolane from reactionof 3,6-dioxaoctane-1,8-dithiol (0.72 g, 1 eq.), lithium hydroxidemonohydrate (0.33 g, 2 eq.), and sulfur (1.02 g, 8 eq.) in 1,3-dioxolane(10 mL).

Example 10 Synthesis of Lithium n-Dodecylpolythiolate from the LithiumAlkyl Mercaptide

To a nitrogen degassed slurry of lithium n-dodecyl mercaptide (0.21 g, 1eq.) in 1,3-dioxolane (5 mL) was added sulfur (0.13 g, 4 eq.). Themixture was stirred under nitrogen at room temperature for 16 hrs.Insoluble solids were removed by filtration. The dark red filtratecontained 63% of lithium n-dodecyl polythiolates and 37% of a mixture ofbis(n-dodecyl)polysulfides as determined by LCMS.

Example 11 Synthesis of Lithium n-Dodecylpolythiolate with Lithium Metaland Sulfur

To a nitrogen degassed solution of n-dodecyl mercaptan (2.23 g, 1 eq.)in 1,3-dioxolane (25 mL) was added sulfur (1.41 g, 4 eq.), and lithium(76.5 mg). The mixture was heated to 60° C. and stirred under nitrogenat 60° C. for 1 hr. Lithium n-dodecyl polythiolate in 1,3-dioxolane wasobtained as a dark red solution. Complete conversion of n-dodecylmercaptan was confirmed by ¹³C-NMR.

Example 12 Synthesis of Lithium 3,6-Dioxaoctane-1,8-Polythiolate withLithium Metal and Sulfur

Following the procedure in Example 11, a dark red solution of lithium3,6-dioxaoctane-1,8-polythiolate in 1,3-dioxolane was obtained byreaction of 3,6-dioxaoctane-1,8-dithiol (1.97 g, 1 eq.), lithium metal(0.15 g, 2 eq.), and sulfur (2.77 g, 8 eq.) in 1,3-dioxolane (11 mL).Complete conversion of starting di-mercaptan was confirmed by ¹³C-NMR

Example 13 Dissolution of Li₂S by Added Lithium n-Dodecylpolythiolate

To determine the solubility of lithium sulfide in electrolyte withlithium n-dodecylpolythiolate, a saturated solution of lithium sulfidewas prepared as follows: A 0.4 M solution of lithiumn-dodecylpolythiolate in 1,3-dioxolane was prepared following proceduresdescribed in Example 10. The solution was then diluted to 0.2 M withtetraethylene glycol dimethyether, then added to 1M LiTFSI solution in1:1 tetraethylene glycol dimethylether: 1,3-dioxolane at 1:1=v/v. To theresulting solution, lithium sulfide was added until a saturated mixturewas obtained. The mixture was then filtered and the filtrate wasanalyzed for dissolved lithium by ICP-MS (Agilent 7700×ICP-MS). Thesolubility of lithium sulfide was calculated based on the lithium level.In 0.5 M LiTFSI with 0.1 M lithium n-dodecylpolythiolate in 1:1tetraethylene glycol dimethylether: 1,3-dioxolane, solubility of lithiumsulfide was determined to be 0.33 wt %. In contrast, without lithiumn-dodecylpolythiolate, the solubility of lithium sulfide in 0.5 M LiTFSIwas only 0.13 wt %. This clearly demonstrated the improved solubility ofLi₂S in the electrolyte matrix of the battery when the organosulfurs ofthis invention are present.

1. A battery, comprising: a) an anode comprising an anode activematerial comprising sodium, lithium or an alloy or composite of at leastone of sodium or lithium with at least one other metal for providingions; b) a cathode comprising a cathode active material comprisingelemental sulfur, elemental selenium or a mixture of elementalchalcogens; and c) an intermediate separator element positioned betweenthe anode and cathode acting to separate liquid or gel electrolytesolutions in contact with the anode and cathode, through which metalions and their counterions move between the anode and cathode duringcharge and discharge cycles of the battery; wherein the liquid or gelelectrolyte solutions comprise a nonaqueous polar aprotic solvent orpolymer and a conductive salt and at least one of conditions (i), (ii)or (iii) are met: (i) at least one of the liquid or gel electrolytesolutions additionally comprise at least one organosulfur species; (ii)the cathode is additionally comprised of at least one organosulfurspecies; (iii) the intermediate separator element comprises afunctionalized porous polymer containing at least one organosulfurspecies; wherein the organosulfur species comprises at least one organicmoiety and at least one —S—S_(n)— linkage, n being an integer of 1 ormore.
 2. The battery of claim 1, wherein the organosulfur species isselected from the group consisting of organic polysulfides and organicpolythiolates and mixtures thereof.
 3. The battery of claim 1, whereinthe organosulfur species contains one or more sulfur-containingfunctional groups selected from the group consisting of dithioacetal,dithioketal, trithio-orthocarbonate, thiosulfonate [—S(O)₂—S—],thiosulfinate [—S(O)—S—], thiocarboxylate [—C(O)—S-], dithiocarboxylate[—C(S)—S-], thiophosphate, thiophosphonate, monothiocarbonate,dithiocarbonate, and trithiocarbonate.
 4. The battery of claim 1,wherein the organosulfur species is selected from the group consistingof aromatic polysulfides, polyether-polysulfides, polysulfide-acid saltsand mixtures thereof.
 5. The battery of claim 1, wherein theorganosulfur species is an organic polysulfide of formula R¹—S—S_(n)—R²,wherein R¹ and R² independently represent a C₁-C₂₀ organic moiety thatmay be linear, branched, or cyclic aliphatic or aromatic and that mayoptionally comprise one or more functional groups containing N, O, P, S,Se, Si, Sn, halogen and/or metal, and n is an integer of 1 or more. 6.The battery of claim 1, wherein the organosulfur species is an organicthiolate of formula R¹—S-M or organic polythiolate of formulaR¹—S—S_(n)-M, wherein R¹ is a C₁-C₂₀ organic moiety that may be linear,branched, or cyclic aliphatic or aromatic and that may optionallycomprise one or more functional groups containing N, O, P, S, Se, Si,Sn, halogen and/or metal, M is lithium, sodium, quaternary ammonium, orquaternary phosphonium, and n is an integer of 1 or more.
 7. The batteryof claim 1, wherein the organosulfur species is a dithioacetal ordithioketal of formulas (I) or (II), or a trithio-orthocarboxylate offormula (III):

wherein each R³ is independently H or a C₁-C₂₀ organic moiety that maybe linear, branched, or cyclic aliphatic or aromatic and that mayoptionally comprise one or more functional groups containing N, O, P, S,Se, Si, Sn, halogen and/or metal, o, p and q are each independently aninteger of 1 or more, and each Z is independently: a C₁-C₂₀ organicmoiety that may be linear, branched, or cyclic aliphatic or aromatic andthat may optionally comprise one or more functional groups containing N,O, P, S, Se, Si, Sn, halogen and/or metal; Li; Na; quaternary ammonium;or quaternary phosphonium.
 8. The battery of claim 1, wherein theorganosulfur species is an aromatic polysulfide of formula (IV), apolyether-polysulfide of formula (V), a polysulfide-acid salt of formula(VI), or a polysulfide-acid salt of formula (VII):

wherein R⁴ independently is tert-butyl or tert-amyl, R⁵ independently isOH, OLi or ONa, and r is 0 or more in formula (IV) with the aromaticrings being optionally substituted in one or more positions withsubstituents other than hydrogen, R⁶ is a divalent organic moiety informula (VI), R⁵ is a divalent organic moiety in formula (VII), each Zis independently a C₁-C₂₀ organic moiety, Li, Na or quaternary ammonium,and o and p are each independently an integer of 1 or more.
 9. Thebattery of claim 1, wherein the organosulfur species is an organo- ororgano-metal polysulfide containing trithiocarbonate functionality offormula (IX), an organo- or organo-metal polysulfide containingdithiocarbonate functionality of formula (X), or an organo- ororgano-metal polysulfide containing monothiocarbonate functionality offormula (XI):

wherein Z is a C₁-C₂₀ organic moiety, Na, Li, quaternary ammonium orquaternary phosphonium, and o and p are each independently an integer of1 or more.
 10. The battery of claim 1, wherein the liquid or gelelectrolyte solution is additionally comprised of a dimetal polythiolatespecies of formula M-S—S_(n)-M, wherein each M is independently Li, Na,quaternary ammonium, or quaternary phosphonium, and n is an integer of 1or more.
 11. The battery of claim 1, wherein the cathode is additionallycomprised of at least one electrically conductive additive and/or atleast one binder.
 12. The battery of claim 1, wherein the organosulfurspecies is pendant to the backbone of the functionalized porous polymer.13. The battery of claim 1, wherein the organosulfur species iscrosslinked into or forms part of the backbone of the functionalizedporous polymer.
 14. The battery of claim 1, wherein the organic moietycontains at least two carbon atoms.
 15. The battery of claim 1, whereinthe intermediate porous separator separates the battery to provide ananolyte section associated with the anode and a catholyte sectionassociated with the cathode and wherein the organosulfur species ispresent in at least one of the anolyte section or the catholyte section.16. The battery of claim 1, wherein the non-aqueous polar aproticsolvent or polymer contains one or more functional groups selected fromether, carbonyl, ester, carbonate, amino, amido, sulfidyl [—S-],sulfinyl [—S(O)—], or sulfonyl [—SO₂-].
 17. The battery of claim 1,wherein the conductive salt corresponds to formula MX wherein M is Li,Na or quaternary ammonium and X is (CF₃SO₂)₂N, CF₃SO₃, CH₃SO₃, ClO₄,PF₆, NO₃, AsF₆ or halogen.
 18. The battery of claim 1, wherein theorganic moiety is oligomeric or polymeric and the organosulfur speciescomprises at least one —S—S— linkage that is pendant to the backbone ofthe oligomeric or polymeric organic moiety.
 19. The battery of claim 1,wherein the organic moiety is oligomeric or polymeric and theorganosulfur species comprises at least one —S—S— linkage that inincorporated into the backbone of the oligomeric or polymeric organicmoiety.
 20. An electrolyte, comprising at least one nonaqueous polaraprotic solvent or polymer, at least one conductive salt, and at leastone organosulfur species comprised of at least one organic moiety and atleast one —S—S_(n)— linkage wherein n is an integer of 1 or more.
 21. Acathode comprising a) elemental sulfur, elemental selenium or a mixtureof elemental chalcogens, b) at least one electrically conductiveadditive, c) and at least one organosulfur species comprising at leastone organic moiety and at least one —S—S_(n)— linkage, n being aninteger of 1 or more.
 22. The cathode of claim 21, in combination with acurrent collector.
 23. The cathode of claim 21, wherein the at least oneelectrode conductivity enhancing agent includes graphite, carbonnanotubes, carbon nanofibers, graphene, carbon black or soot.
 24. Thecathode of claim 21, additionally comprising at least one binder.